1. Technical Field
The present invention relates generally to power limiting and, more particularly, to technology for limiting the power used by each multi-core processor in a symmetric multiprocessing system in consideration of energy efficiency and QoS.
2. Description of the Related Art
Power capping is technology for limiting the power actually consumed by a system to a power limit value (a power cap value), which is set by a user or an administrator.
Such power capping is mainly used for servers in an Internet Data Center (IDC), in which a large amount of power is used, and may be applied in order to limit the maximum power consumption so as not to exceed the amount of power that can be supplied by a power supply device when all of the servers consume the maximum power at the same time. Power capping may also be applied when the power required by a server is not sufficiently supplied due to failure of power supply hardware or the like.
Meanwhile, power capping may be implemented by two methods, namely, one method in which a power supply unit mounted on a computing system limits the total power consumption, and another method in which the power used by various devices in a computing system, such as a CPU, memory, an input/output device, and the like, is limited. Particularly, a technique for limiting the power used by a CPU, which consumes the greatest amount of power in the computing system, is applied most often.
Basically, power capping is configured such that the total power consumption of a system is measured and compared with a power usage value (a power cap value) set by a user. If the total power consumption is greater than the power cap value, the power consumption of the entire system or of components, the power consumption of which can be regulated, is limited.
However, according to this conventional power capping method, when the function of limiting power is performed, power consumption is reduced, thus causing a decrease in performance. Also, the performance decrease may lead to a delay in processing concurrent tasks. That is, because the conventional power capping methods do not consider the increase in processing time that results from the performance decrease when power is limited, additional energy consumption may result.
Also, in the case of a Symmetric Multiprocessing (SMP) system, which is a high-performance system having multiple CPUs, the conventional power-limiting method sets a constant power cap value regardless of the number of CPUs. If the power cap value is set without regard to the number of CPUs in the SMP system, when the CPU utilization rate of only some of the multiple cores is high, energy efficiency may decrease. Also, when various kinds of loads are processed by the system and each of the loads requires a different level of Quality of Service (QoS), the desired QoS may not be provided.
Therefore, new power capping technology that may maximize energy efficiency and provide desired QoS in an SMP system is required.
In connection with this, Korean Patent Application Publication No. 10-2010-0071913, discloses a technology related to “Method and arrangement for limiting electric power required by electric loads.”